Rapid species identification of pygmy rabbits (Brachylagus idahoensis) from faecal pellet DNA

The pygmy rabbit (Brachylagus idahoensis) is a small lagomorph of the western United States that specializes in sagebrush (Artemisia spp.) habitat. Intensive habitat loss and modification have increased the vulnerability of pygmy rabbit populations, but the current geographic distribution and population status remain unclear. To aid in detection and population monitoring, we developed a species identification test that uses mitochondrial DNA species-specific primers to distinguish among six sympatric lagomorph species using DNA isolated from faecal pellets. Applying this test, we successfully identified the species of origin for all pellet samples that produced a positive PCR result (77% of 283 pellets collected). Pellets collected during the winter (December-February) had higher PCR success rate (93%) than pellets collected at other times of the year (72%). This test, using non-invasive genetic sampling of faecal pellets, provides an efficient method for assessing site occupancy and distribution of pygmy rabbits and other lagomorphs across large geographic areas.     

Spatio-Temporal Factors Shaping Diurnal Space Use by Pygmy Rabbits

Abstract: Factors influencing patterns of space use by pygmy rabbits (Brachylagus idahoensis) are poorly understood. We studied diurnal space use by adult pygmy rabbits during multiple breeding and nonbreeding seasons at 3 sites in the Lemhi Valley, Idaho, USA, during 2004–2005. Pygmy rabbits used larger areas than predicted by allometric models and documented by some previous investigations. Sex and season strongly influenced space use by rabbits. Males used larger home ranges and core areas, more burrow systems, and more widely dispersed burrow systems than did female rabbits. We also documented significant differences among study sites in many movement parameters, which suggested that local resource distribution also might influence how pygmy rabbits use space. Our results indicated that pygmy rabbits use large areas and exhibit seasonal, sex, and site-specific variation in patterns of movement and space use. Therefore, larger areas of habitat may be needed to conserve pygmy rabbits to accommodate seasonal, regional, and potentially annual variation in resource availability and to maintain linkages among populations.     

Sagebrush Characteristics Influencing Foraging Patterns of Pygmy Rabbits

The pygmy rabbit (Brachylagus idahoensis) is endemic to the sagebrush steppe landscapes in the western United States. Pygmy rabbits have adapted to this region by depending on big sagebrush (Artemisia tridentata) as a source of nutrition and concealment from predators. Being a central place forager, and a dietary specialist makes pygmy rabbits an ideal subject to study foraging tradeoffs. Our objectives were to determine if pygmy rabbit foraging patterns are influenced by the nutrient content of individual sagebrush, or the size and location of individual sagebrush. We first developed a near infrared spectroscopy assay that can be conducted in the field, with whole plant foliage, to determine individual sagebrush crude protein (CP) and acid detergent fiber (ADF) contents. We then measured the size, location, protein, and fiber contents of >1,500 foraged and non-foraged sagebrush plants surrounding pygmy rabbit burrows in 2 field sites in northern Utah, USA. We found significant site differences in sagebrush CP levels and significant season differences in sagebrush ADF levels; sagebrush closer to central burrows were higher in protein and lower in fiber. Pygmy rabbits preferred to forage on taller sagebrush plants that were closer to the central burrow but only marginally higher in CP (0.2%) and lower in ADF (1%). Sagebrush plants with a >50% chance of being foraged, were <5.6 m from the burrow, >0.67 m tall, >10.4% CP, and <34.95% ADF. The selection of closer, larger, and more nutrient-dense sagebrush may be influenced by pygmy rabbits' need for concealment from predators or a way to minimize foraging effort. © 2020 The Wildlife Society.     

Habitat selection of feral cats (Felis catus) on a temperate,forested island

Abstract Habitat selection of mammalian predators is known to be influenced by availability and distribution of prey. The habitat selection of feral cats on Stewart Island, southern New Zealand, was investigated using telemetry of radio‐tagged cats. Compositional analysis of the habitat selection of radio‐tagged cats showed they were using the available habitats non‐randomly. Feral cats avoided subalpine shrubland and preferentially selected podocarp‐broadleaf forest. The avoidance of subalpine shrubland by cats was probably due to a combination of the presence of a large aggressive prey species, Norway rats Rattus norvegicus, and the lack of rain‐impervious shelter there. Most cats also used subalpine shrubland more often in dry weather than in wet weather. Cats did not preferentially select all the other habitats with only smaller rat species, Rattus rattus and Rattus exulans, present however. Cats were probably further influenced by the availability of large trees, in podocarp‐broadleaf forest, that can provide shelter. Cats were also more active in dry rather than wet weather which supports this conclusion. Home ranges of feral cats on Stewart Island were some of the largest recorded, probably because of limited primary and alternative prey.     

An Examination of Scale-Dependent Resource Use by Eastern Hognose Snakes in Southcentral New Hampshire

ABSTRACT The decline of many snake populations is attributable to habitat loss, and knowledge of habitat use is critical to their conservation. Resource characteristics (e.g., relative availability of different habitat types, soils, and slopes) within a landscape are scale-dependent and may not be equal across multiple spatial scales. Thus, it is important to identify the relevant spatial scales at which resource selection occurs. We conducted a radiotelemetry study of eastern hognose snake (Heterodon platirhinos) home range size and resource use at different hierarchical spatial scales. We present the results for 8 snakes radiotracked during a 2-year study at New Boston Air Force Station (NBAFS) in southern New Hampshire, USA, where the species is listed by the state as endangered. Mean home range size (minimum convex polygon) at NBAFS (51.7 ± 14.7 ha) was similar to that reported in other parts of the species’ range. Radiotracked snakes exhibited different patterns of resource use at different spatial scales. At the landscape scale (selection of locations within the landscape), snakes overutilized old-field and forest edge habitats and underutilized forested habitats and wetlands relative to availability. At this scale, snakes also overutilized areas containing sandy loam soils and areas with lower slope (mean slope = 5.2% at snake locations vs. 6.7% at random locations). We failed to detect some of these patterns of resource use at the home range scale (i.e., within the home range). Our ability to detect resource selection by the snakes only at the landscape scale is likely the result of greater heterogeneity in macrohabitat features at the broader landscape scale. From a management perspective, future studies of habitat selection for rare species should include measurement of available habitat at spatial scales larger than the home range. We suggest that the maintenance of open early successional habitats as a component of forested landscapes will be critical for the persistence of eastern hognose snake populations in the northeastern United States.     

Leveraging multidimensional heterogeneity in resource selection to define movement tactics of animals

Increasing interest in the complexity, variation and drivers of movement‐related behaviours promise new insight into fundamental components of ecology. Resolving the multidimensionality of spatially explicit behaviour remains a challenge for investigating tactics and their relation to niche construction, but high‐resolution movement data are providing unprecedented understanding of the diversity of spatially explicit behaviours. We introduce a framework for investigating individual variation in movement‐defined resource selection that integrates the behavioural and ecological niche concepts. We apply it to long‐term tracking data of 115 African elephants (Loxodonta africana), illustrating how a behavioural hypervolume can be defined based on differences between individuals and their ecological settings, and applied to explore population heterogeneity. While normative movement behaviour is frequently used to characterise population behaviour, we demonstrate the value of leveraging heterogeneity in the behaviour to gain greater insight into population structure and the mechanisms driving space‐use tactics.     

Effects of origin and experience on patterns of host acceptance by the opiine parasitoid Diachasmimorpha tryoni

1. Patterns of host acceptance by Diachasmimorpha tryoni (Ashmead), a parasitoid of tephritid flies, were evaluated in relation to host–substrate complex, wasp origin, and wasp experience. 2. Naive female D. tryoni originating both from the Mediterranean fruit fly (medfly) Ceratitis capitata (Wiedemann) and the lantana gall fly Eutreta xanthochaeta Aldrich probed medfly-infested coffee fruit two to six times more often than E. xanthochaeta-inhabited lantana galls. No significant differences were detected between the two groups of parasitoids in patterns of probing response to medfly-infested coffee fruit or to E. xanthochaeta galls. 3. An 18-h pretest exposure to medfly-infested coffee fruit or E. xanthochaeta-inhabited galls affected the probing response of D. tryoni to E. xanthochaeta galls significantly, but did not affect the probing response to medfly-infested coffee fruit. Diachasmimorpha tryoni exposed to E. xanthochaeta galls probed E. xanthochaeta galls two to three times more often than naive wasps, and seven to 11 times more than wasps exposed to medfly-infested coffee fruit. Regardless of the prior exposure treatments, a high proportion (75–100%) of the test parasitoids probed medfly-infested coffee fruit. 4. Parasitoid acceptance of less-preferred hosts or host–substrate complexes may be more amenable to conditioning through prior experience (i.e. learning) than preferred host–substrate complexes. The relevance of these findings to host range expansion of parasitoids used in fruit fly biological control is discussed.     

Effects of a fire-retardant on oviposition habitat selection and larval development of the mosquito Culiseta longiareolata

1. Fire retardants are composed of fertilising salts that are commonly used for fighting wildfires. These chemicals have various effects on individual arthropod species and aquatic communities. 2. This study investigated the effects of four treatments of a prevalent fire retardant [FR CROS 134 (FR), applied at concentrations of 0, 3.8 × 10², 7.6 × 10² and 11.4 × 10² mg litre⁻¹] on oviposition habitat selection (OHS) by Culiseta longiareolata and Culex laticinctus mosquitoes in an outdoor mesocosm. Additionally, larval development of C. longiareolata was examined in response to this fire retardant. 3. The results demonstrate that OHS increased in both species, whereas survivorship (0–86.7%) and time to metamorphosis (5.4–23.1 days) of C. longiareolata were not affected by any of the treatments. However, cyanobacterial biomass increased and heterotrophic bacteria decreased in response to the addition of FR. 4. It was found that FR applications can have unintended consequences which can increase OHS by female mosquitoes. The growing use of fire retardants worldwide, and especially in Israel, justify evidence-based assessment and environmental management of their use. This study is a first critical step in filling the knowledge gap with respect to the impact of FR on aquatic ecosystems.     

Effects of Anisops sardea (Hemiptera: Notonectidae) on oviposition habitat selection by mosquitoes and other dipterans and on community structure in artificial pools

We investigated the effects of the predatory backswimmer, Anisops sardea, on oviposition habitat selection of mosquitoes and other dipterans, and on community structure in experimental pools. We predicted that those dipteran species whose larvae were shown to be highly vulnerable to predation by Anisops would avoid Anisops pools when choosing an oviposition site. We established the following treatments in plastic tubs: (1) Control (without Anisops); (2) Free Anisops (ten Anisops within pool but not caged); (3) Caged Anisops (ten Anisops in cage). The pools were open to colonization by insects. We added resting stages of crustaceans and first instar larvae of the mosquitoes Culiseta longiareolata and Culex laticinctus. Among the dipteran species, Culiseta longiareolata, Culex laticinctus, Chironomus riparius (Chironomidae) and Forcipomyia sp. (Ceratopogonidae), only Culisetalarvae were highly vulnerable to predation. As predicted, based on larval vulnerability, Culiseta, but not the other species, avoided Anisops pools when ovipositing. Free Anisops reduced taxon richness. This reduction resulted largely from the elimination of the cladoceran Ceriodaphniasp. and Culiseta in most free Anisops pools. Thus, Anisops sardea structures the community, both by a behavioral response of prey to its presence and by consumption of prey.     

不同杀虫剂选育对家蝇抗药性水平及kdr基因频率的影响

采用杀虫剂（溴氰菊酯和甲基嘧啶磷）筛选及不接触药物自然衰退的方法,研究了家蝇Musca domestica氯氟氰菊酯高抗品系(Cyh-R)对杀虫剂的抗性变化,探讨蝇类抗药性治理的方法。用点滴法测定氯氟氰菊酯对不同家蝇品系的毒力,比较抗药性的变化,结合特异性等位基因PCR扩增（PASA）技术检测了不同家蝇品系的kdr基因频率,探讨kdr基因频率与抗性水平之间的关系。结果表明:甲基嘧啶磷筛选后,氯氟氰菊酯对第2~8代Cyh-R品系的LD₅₀呈递减趋势,从F₀的2.8434 μg/蝇降为F₈的0.4404 μg/蝇,但第8~18代Cyh-R品系的LD₅₀呈逐代递增趋势;溴氰菊酯筛选后,氯氟氰菊酯对Cyh-R品系第2~16代的LD₅₀呈上升趋势,从F₀的2.8434 μg/蝇升至F₁₆的24.3249 μg/蝇;表明了施用有机磷杀虫剂可降低其对氯氟氰菊酯的抗药性,而施用拟除虫菊酯药剂则有助于其对氯氟氰菊酯抗药性的增长;不使用任何杀虫剂也能降低其对氯氟氰菊酯的抗药性,但下降速率低于甲基嘧啶磷。PASA技术检测表明Cyh-R品系的kdr抗性基因频率为88.8%,不经过任何药剂筛选其kdr抗性基因频率下降程度最大,达到69.7%;甲基嘧啶磷筛选后其结果降为78.8%,而经溴氰菊酯筛选后kdr抗性基因频率则明显升高,达到98.9%。通过对kdr抗性基因频率和抗性水平进行相关和回归分析表明kdr抗性基因频率与家蝇对氯氟氰菊酯的LD₅₀呈对数关系,即LD₅₀值高的品系其kdr抗性基因频率相应的也较高。建议在家蝇防治中考虑轮换用药。     

Effects of organic and conventional fertilizer treatments on host selection by the aphid parasitoid Diaeretiella rapae

The type and quantity of fertilizer supplied to a crop will differ between organic and conventional farming practices. Altering the type of fertilizer a plant is provided with can influence a plant’s foliar nitrogen levels, as well as the composition and concentration of defence compounds, such as glucosinolates. Many natural enemies of insect herbivores can respond to headspace volatiles emitted by the herbivores’ host plant in response to herbivory. We propose that manipulating fertilizer type may also influence the headspace volatile profiles of plants, and as a result, the tritrophic interactions that occur between plants, their insect pests and those pests’ natural enemies. Here, we investigate a tritrophic system consisting of cabbage plants, Brassica oleracea, a parasitoid, Diaeretiella rapae, and one of its hosts, the specialist cabbage aphid Brevicoryne brassicae. Brassica oleracea plants were provided with either no additional fertilization or one of three types of fertilizer: Nitram (ammonium nitrate), John Innes base or organic chicken manure. We investigated whether these changes would alter the rate of parasitism of aphids on those plants and whether any differences in parasitism could be explained by differences in attractivity of the plants to D. rapae or attack rate of aphids by D. rapae. In free‐choice experiments, there were significant differences in the percentage of B. brassicae parasitized by D. rapae between B. oleracea plants grown in different fertilizer treatments. In a series of dual‐choice Y‐tube olfactometry experiments, D. rapae females discriminated between B. brassicae‐infested and undamaged plants, but parasitoids did not discriminate between similarly infested plants grown in different fertilizer treatments. Correspondingly, in attack rate experiments, there were no differences in the rate that D. rapae attacked B. brassicae on B. oleracea plants grown in different fertilizer treatments. These findings are of direct relevance to sustainable and conventional farming practices.